scholarly journals Aerodynamic characteristics of a square cylinder with corner fins

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Qiulei Wang ◽  
Qi Jiang ◽  
Gang Hu ◽  
Xiao Chen ◽  
Chao Li ◽  
...  

AbstractThis paper investigates the effect of fitting fins at the corners of a square cylinder on aerodynamic characteristics of the cylinder via wind tunnel tests and large eddy simulations (LES). Although it has been recognized that the corner fins have a remarkable effect on aerodynamic characteristics of a square cylinder, no study has been carried out to systematically evaluate this effect and reveal the underlying mechanism. Three types of corner fin configurations, i.e. fins fitted only to the leading corners, fins fitted only to the trailing corners, and fins fitted to both leading and trailing corners were studied. It was found that the corner fins significantly influence aerodynamic characteristics, such as mean drag coefficient, fluctuating lift coefficient, and vortex shedding of the cylinder. The influences of these corner fin configurations are very different. In general, the leading and trailing fins have an opposite effect on these characteristics. The mechanisms underlying these effects were clarified based on the flow regime visualized via LES. The interesting findings have practical significances not only for reducing aerodynamic forces and wind-induced vibration of infrastructures, but also for enhancing wind-induced vibration-based energy harvesting.

2011 ◽  
Vol 110-116 ◽  
pp. 4269-4275
Author(s):  
K. Lam ◽  
Y.F. Lin ◽  
Y. Liu ◽  
L. Zou

The effect of the wavy surface on the aerodynamic characteristics of an airfoil is studied using the large eddy simulations. A more gentle lift characteristic is obtained during stall. For angles of attack less than the baseline stall angle of a NACA0012 airfoil, a lift coefficient reduction was observed for the wavy airfoils, while the lift coefficient increases up to 23% greater than that of a NACA0012 airfoil when the angle of attack is larger than the baseline stall angle of the NACA0012 airfoil.


2017 ◽  
Vol 813 ◽  
pp. 23-52 ◽  
Author(s):  
Rafael Pérez-Torró ◽  
Jae Wook Kim

A numerical investigation on the stalled flow characteristics of a NACA0021 aerofoil with a sinusoidal wavy leading edge (WLE) at chord-based Reynolds number $Re_{\infty }=1.2\times 10^{5}$ and angle of attack $\unicode[STIX]{x1D6FC}=20^{\circ }$ is presented in this paper. It is observed that laminar separation bubbles (LSBs) form at the trough areas of the WLE in a collocated fashion rather than uniformly/periodically distributed over the span. It is found that the distribution of LSBs and their influence on the aerodynamic forces is strongly dependent on the spanwise domain size of the simulation, i.e. the wavenumber of the WLE used. The creation of a pair of counter-rotating streamwise vortices from the WLE and their evolution as an interface/buffer between the LSBs and the adjacent fully separated shear layers are discussed in detail. The current simulation results confirm that an increased lift and a decreased drag are achieved by using the WLEs compared to the straight leading edge (SLE) case, as observed in previous experiments. Additionally, the WLE cases exhibit a significantly reduced level of unsteady fluctuations in aerodynamic forces at the frequency of periodic vortex shedding. The beneficial aerodynamic characteristics of the WLE cases are attributed to the following three major events observed in the current simulations: (i) the appearance of a large low-pressure zone near the leading edge created by the LSBs; (ii) the reattachment of flow behind the LSBs resulting in a decreased volume of the rear wake; and, (iii) the deterioration of von-Kármán (periodic) vortex shedding due to the breakdown of spanwise coherent structures.


2020 ◽  
Vol 10 (5) ◽  
pp. 1870
Author(s):  
Zhongying Xiong ◽  
Xiaomin Liu

This work focuses on flow past a circular cylinder at a subcritical Reynolds number. Although this classical study has been a concern for many years, it is still a challenging task due to the complexity of flow characteristics. In this paper, a high-efficiency very large-eddy simulation method is adopted and verified in order to handle the oscillating boundary. A series of numerical simulations are conducted to investigate the transient flow around the oscillating cylinder. The results show that the vortex shedding mode varies with an increase in the excitation amplitude and the excitation frequency. Vortex shedding is a lasting process under the condition of a low excitation amplitude that leads to irregular fluctuations of the lift and drag coefficients. For a vortex shedding mode that exhibits a strong vortex pair and a weak vortex pair or a weak single vortex, the temporal evolution of the lift coefficient of the oscillating cylinder shows irregular ”jumping” at a specific time per cycle corresponding to the shedding of the strong vortex pair. The vortex shedding mode and the frequency and time of the vortex shedding co-determine the temporal evolutions of the lift and drag coefficient.


2017 ◽  
Vol 27 (10) ◽  
pp. 2355-2374 ◽  
Author(s):  
Sajjad Miran ◽  
Chang Hyun Sohn

Purpose The paper aims to study the influence of rounded corners on the flow-induced oscillation of a square cylinder that is free to oscillate in two degrees of freedom. Design/methodology/approach The finite volume code in conjunction with the moving mesh scheme was implemented via a user-defined function to carry out the computations in two dimensions. The Reynolds number (Re) chosen for the present study is fixed at 100, and the frequency ratio, Fr = fs/fn (where fs is the vortex shedding frequency and fn is the natural frequency of cylinder) is used as a varying parameter. The computational model was validated for flow past a stationary cylinder with R/D = 0 and 0.5, and the results showed good agreement with the literature. Findings The aerodynamic characteristics, amplitude response, trajectories of cylinder motion and vortex shedding modes are obtained by conducting a series of simulations under different frequency ratios of the cylinder. It was found that the minimum transverse amplitude, drag force and lift force obtained for a naturally oscillating square cylinder are quite different when compared with a stationary and forced oscillating cylinder, where the maximum drag and lift forces were observed for a square cylinder and a minimum around R/D = 0.2 was observed. Originality/value The present work identified the significant effect of the varying frequency ratio and R/D on the VIV modes of the cylinder. It was observed that the cylinder wake exhibits the (2S) vortex shedding mode for R/D = 0 to 0.2 at all Fr, whereas the C (2S) mode appeared for R/D > 0.2 at Fr = 1.1.


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